1. Field of the Invention
The present invention relates to a thin film forming apparatus for forming a thin film on a substrate using a sheet film, and a film supplying mechanism, a film cassette, a transportation mechanism and a transportation method which can be used in such an apparatus.
2. Description of the Related Art
Over the recent years, it has became necessary to use a thin film forming method suitably applicable to a large area size as wafers used during manufacturing of LSIs have became larger in diameter, liquid crystal panels have became larger in area size, etc. In addition, in the field of multilevel interconnection techniques among techniques for manufacturing LSIs, the surface of an insulation film needs be planarized accurately to realize multilevel interconnections. Hence, there are increasing demands for larger area sizes and better surface planarization techniques for planarization of surfaces during fabrication of thin films. In an effort to meet these demands, thin film forming techniques for forming a thin film on a substrate by a pressure transfer method have been proposed.
This type of thin film forming apparatus may be an apparatus which is described in Japanese Patent Application Laid-Open Gazette No. 2001-135634 for instance. In this apparatus, a thin film is disposed on a substrate in accordance with thin film forming steps that are shown in FIGS. 18A through 18D. First, as shown in FIG. 18A, a substrate W, such as a semiconductor wafer and a glass substrate for liquid crystal panel, is placed on a specimen holder in such a manner that electrode interconnections 111 formed on a surface of the substrate W direct themselves toward above. In this example, the surface 112 seating the electrode interconnections 111 serves as a thin film bearing surface on which a thin film is to be disposed through steps described below.
Next, as shown in FIG. 18B, a sheet film F whose surface already seats an insulation film 121 is mounted to a transfer plate which is located above the specimen holder to face the specimen holder. In this example, the insulation film 121 is the thin film that is to be transferred onto the substrate W. The insulation film 121 is located so as to face the thin film bearing surface 112 of the substrate W that is placed on the specimen holder. The specimen holder is moved toward the transfer plate and the substrate W and the sheet film F are accordingly brought into contact with each other. Thereafter, the substrate W and the sheet film F are pressed against each other as denoted at the arrows in FIG. 18B for a certain period of time while heating the substrate W to a predetermined temperature. As a result, the substrate W and the sheet film F tightly adhere to each other with the insulation film 121 inserted between the two, and a tightly adhered object is obtained.
The tightly adhered object is taken out from a thin film forming chamber and the sheet film F is peeled off as shown in FIG. 18C, whereby the substrate W which seats the insulation film 121 as that shown in FIG. 18D is obtained.
By the way, for the purpose of forming a thin film using the apparatus described above, it is necessary to retrieve a pre-transfer substrate out from a substrate cassette and place the same on a specimen holder. The other hand, it is necessary to retrieve an unused sheet film F out from a film cassette and apply a surface of the sheet film F with the insulation film 121 using a coating apparatus. Furthermore, the film F with the insulation film 121 is placed on a transfer stage of the thin film forming apparatus. It is also necessary, after transfer, to retrieve the tightly adhered object bearing the transferred thin film (which is obtained by joining the substrate W and the sheet film F through the insulation film 121) out from the thin film forming apparatus, and thereafter peel off only the sheet film F from the tightly adhered object using a peeling apparatus of the thin film forming apparatus. The sheet film F and/or the substrate W are thus transported between the respective apparatuses. The transportation of the sheet film F, the substrate W and the like is performed manually by an operator according to conventional techniques. Hence, the processing efficiency is poor, which serves as one of major causes of deterioration in throughput. This has gave rise to a strong demand for efficiently supplying of sheet films, a handling (holding/transporting) technique.
Further, once human operators handle transportation of sheet films, particles may adhere to the sheet films or heat may dissipate from the sheet films. This makes it difficult to control heat histories and leads to deterioration in product quality of thin films and even a drop in production yield, which is a problem. There is another problem that a large floor space is necessary to install the apparatus. While automated transportation of sheet films is indispensable to solve these problems, there has been no handling technique that is suitable to such automation.